PARIS, April 3 (Reuters) - French health authorities on Thursday put doctors and hospitals on alert to report any signs that an Ebola virus outbreak affecting West Africa had infected patients in France, though no symptoms had yet been detected.

France maintains close relations with several former colonies in the region, with immigrants and the employees of French multinational firms travelling frequently back and forth.

An outbreak of the disease - which has a fatality rate of up to 90 percent - originated in Guinea two months ago and has spread to neighbouring Libera and Sierra Leone, while Gambia has placed two people in quarantine.

"We have put doctors in France on alert so that they will think of this disease if they come across certain symptoms," Health Minister Marisol Touraine told i>Tele television.

The move was preventative and not been prompted by the detection of any symptoms, she added.

Further instructions were sent to health authorities in the larger Paris region regarding passengers arriving at the Charles de Gaulle international airport, though no measures had yet been taken to restrict travel. (Reporting by Chine Labbe and Nicholas Vinocur; Editing by Andrew Callus and Alison Williams)

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